Automated Batch Control of Delayed Coker

ABSTRACT

An automatic batch sequence computer control system is configured to automatically operate process valves in a delayed coker for a complete coke drum cycle. Double verification of the movement of the process valves is used to confirm advancing to the next step. Primary verification is achieved by using position sensors on the valves. Secondary verification is achieved by using monitored process conditions and confirming the measured conditions correlate with expected process conditions for an arrangement of valve positions at a given sequence in the coke drum cycle. A safety interlock system may be integrated with the control system.

BACKGROUND

A delayed coker is a unit that thermally converts vacuum distillationcolumn bottoms residue product into lighter distillate and coke. Thecoking process is primarily a semi-batch process with two or more cokedrums operating in pairs in alternating cycles—one drum is filled whilethe other is emptied. Typically, one coke drum is filled with a batch ofheated feed material, such as vacuum distillation column bottoms residueproduct (also known as “vacuum resid”), that has been heated to a hightemperature, between about 830 to 950 degrees Fahrenheit (“° F.”), at alow pressure, between about 15 to 60 pounds per square inch gauge(“psig”). The batch of feed material is allowed to thermally react inthe coke drum for a period of time. The gaseous reaction products of thethermal cracking are removed from the top of the coke drum and sent to afractionator. The remaining reaction products remain in the drum andsolidify into a product known as petroleum coke, or simply coke. Thecoke drum is then steamed, cooled and vented, after which the coke drumis opened to the atmosphere and the coke is removed from the drum bycutting it up with high pressure water into small chunks and allowing itto drop out of a large opening at the bottom of the drum. Typically, asingle batch of coke may be formed during one cycle that allows the cokedrum to be filled for a coking period of between 12 to 18 hours. Thus,one complete fill, coke and unload cycle typically will be double thistime.

Originally, this process was operated manually. Human operators wouldopen and close valves manually in a predetermined sequence to route thefeed to one coke drum, while other valves are opened and closed toisolate the other drum that is full of coke product ready to be emptied.The delayed coker unit may include up to twenty or more sets of valvesfor each coke drum, with some valve sets including two valves for adouble-block isolation. As such, it can be a very labor intensiveoperation to open and close the valves in a precise sequence requiredfor safe operation of the delayed coker during each coke drum cycle withvery short times of at most a few hours between each step requiringnumerous valve position changes. Because some valves in the unit are onprocess lines that are exposed to both hydrocarbons and the atmosphereat different parts of the cycle, it is important to avoid exposure ofhot hydrocarbon to oxygen by verifying the right valves are closedand/or open at each step of the process.

Beginning in the 1990's, delayed coker process units began to takeadvantage of automation equipment. Manually operated isolation valveswere replaced with locally operated motor operated valves and thenremotely controlled motor operated valves. Additional double blockvalves for ensured isolation were installed in some locations. Remotelyoperated automated top and bottom deheading valves replaced manuallyoperated deheading valves. Electronic safety interlock systems wereadded to verify valve position and prevent operators from opening thewrong valves or correct valves at the wrong time that might exposeheated hydrocarbons to the atmosphere, or expose the operators to thehot hydrocarbons. Partial automation of portions of a delayer cokeroperation have been proposed. Despite these improvements, the operationof a delayed coker still requires significant labor of human operatorsin the unit.

SUMMARY OF THE INVENTION

One embodiment of the invention is a method for automatic operation of adelayed coker. The method includes providing an automatic batch sequencecontrol system configured to automatically operate process valves in adelayed coker for a complete coke drum cycle. The method carried out bythe control system includes verifying a position of a process valve in afirst step of the sequence before advancing to a next step of is thesequence. Verifying the position for a set of double block valvesincludes a primary and a secondary verification. The primaryverification includes receiving signals from a position sensor on eachof the double block valves that detect that the position of each of thedouble block valve is in the correct open or closed position. Thesecondary verification includes receiving a signal from a pressuretransmitter that the pressure in the process piping between the doubleblock valves is correctly below or above a predetermined thresholddepending on whether the set of double block valves has been commandedto open or close, respectively.

Additional embodiments of the invention and the advantages appurtenantthereto are described in more detail below with reference to theenclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative process flow diagram of a two-drum delayedcoker unit according to one embodiment of the invention.

FIG. 2 is a representative schematic of double block valve and pressurepiping and instrument diagram according to one embodiment of theinvention.

FIG. 3 is a representative logic flow chart for one exemplary step of acoke drum cycle in an automated sequence controller according to oneembodiment of the invention.

FIG. 4 is a schematic representation of an exemplary distributedcomputer control system for automated batch operation of a delayed cokeraccording to one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention may provide several advantages. Abatch sequence controller, as described in more detail below, may beprovided to remotely and automatically operate the valves in a delayedcoker to automatically proceed through an entire coke drum decokingcycle, and to ensure that each previous step is safely completed beforeproceeding to the next step. This may significantly reduce the risk topersonnel by allowing personnel to operate the coke drum unit remotelyfrom the operating room.

Referring to the embodiment of FIG. 1, a representative piping and flowdiagram for a delayed coker with two coke drums in parallel is shown.The diagram include major process lines, automated valves, double blockisolation points and major process measurement points. Connecting withthe bottom of the first coke drum 10, the vacuum residual feed 102 isintroduced through the feed switch valve 104. When filling the firstcoke drum 10, the feed switch valve 104 is open in line with the firstcoke drum 10 and feed isolation valve 106 is open. Steam is supplied toa feed isolation steam valve 108 and a steam sweep valve 110 on the feedline 112. The feed line 112 also has connected to it the common utilityheader valve 114, which is connected to a utility isolation valve 122for isolating a common a utility header for a quench water supply valve116, a steam supply valve 118, and a bottom drain valve 120. The commonutility header valve 114 also connects with the condensate drain doubleblock valves 124 and 126. The common utility header valve 114 is closedwhile the coke drum is being filled with feed.

Connecting with the top of the coke drum 10, the overhead vapor line 128is connected with several valves including the double block overheadquench valves 130 and 132, the vent double block valves 134 and 136, themain vapor double block valves 138 and 140, which connects to thefractionator feed line 144. Also, connected with the overhead vapor line128, are the blowdown double block valves 146 and 148, which include avapor line drain valve 150 directing flow to the blowdown settling drum.Also at the top of the coke drum 10 is an overhead relief line 152,which connects with the pressure relief valve(s) 154 and pressure reliefisolation valve(s) 156 that direct flow to the blowdown. The overheadrelief line 152 also serves as feed line for the antifoam double blockvalves 158 and 160, which direct antifoam additive during the coke drumfilling step.

Various pressure sensor transmitters and temperature sensor transmittersare included throughout the equipment to provide process status inputsto the batch sequence control system. The pressure measurements may beused for secondary verification of the correct valve positions byconfirming the expected process pressures correspond to the expectedpressure given a particular set of valve positions and step in the cokedrum cycle sequence. Likewise, the temperature measurements may be usedto confirm the expected conditions correlate with the expected processtemperature for the defined valve positions for that step in the cokedrum cycle sequence. Accordingly, pressure transmitters may be locatedat the various valve isolation points or between double block valveconfigurations including the feed isolation point 160, the commonutility header isolation point 162, the utility header isolation point164, the condensate drain isolation point 166, the overhead quench lineisolation point 168, the overhead vent isolation point 170, the blowdownisolation point 172, the main vapor isolation point 174, the antifoamisolation point 176 and the pressure relief valve isolation point 178.The delayed coker also may include other process measurementtransmitters including coke drum feed line pressure 180, the coke drumoverhead pressure 182, the coke drum overhead temperature 184 on thevapor line 128, and the vapor line drain line temperature 186.

In the embodiment of FIG. 1, the coke drum includes the top head valve(also known as deheading valve) 188 and the bottom head valve (alsoknown as deheading valve) 190, which are opened only during the cokeunloading phase of the coke drum cycle. These deheading valves may bespecial motor or hydraulic operated slide valves, such as thosemanufactured by DeltaValve, e.g., Models GV320 and GV380, that have lowpressure steam purges in the body to maintain a pressure in the valvebody higher than the process pressure to keep the valves seats and sealsclean, and maintain a positive steam pressure isolation point betweenthe hydrocarbon process environment and the atmosphere. Pressuretransmitters 192 and 194 are included monitoring the steam pressure onthe interior bodies of these valves, respectively. The pressures may bemonitored as secondary verification of the deheading valve positions,because the steam pressure is above a predetermined threshold when thevalves are in the fully closed position.

While the above valves and process measurement transmitters have beendescribed for the first coke drum 10, preferably an identical set ofvalves and process transmitters are used for similar operation of thesecond coke drum 20. Coke drum operations may vary depending on theconfiguration of the equipment and piping and the above description isillustrative of one embodiment.

For safe operations of a delayed coker, hot hydrocarbons should beisolated from exposure to the atmosphere. Double block valves may beused throughout the delayed coker to provide isolation points thatseparate hydrocarbons from oxygen environments. In some embodiments ofthe present invention, the batch sequence control scheme uses bothprimary verification and secondary verification of a valve position aseither open or closed. Although other double block valve configurationsmay be used, a typical double block valve configuration includes twoball valves (or other type of valves, such as gate valves or plugvalves) with a steam pressure purge connected to the process pipingbetween the two valves. The primary verification may include receivingsignals from position sensors on the valves to indicate whether thevalve is open or closed. The secondary verification may includereceiving a process condition transmitted from a point in the processpiping between the two valves. When both valves are closed, the steampurge pressurizes the process piping to a pressure above a predeterminedthreshold. For example, if the steam supply pressure is 100 psig, apressure measurement from a pressure transmitter located on the processpiping between the two valves which exceeds a predetermined threshold,for example, 70 psig, indicates that both valves are closed such thatthe process piping has been pressurized with steam. If one of the valveshas not completely closed, the steam would leak out from between the twovalves and the pressure would not rise above the threshold. Conversely,if both valves are moved from a closed position to an open position, thepressure between the two valves would decrease to below the threshold.Therefore, the pressure between the two valves provides a secondaryverification that the valves have moved from a closed to an openposition or an open to a closed position.

Referring to the embodiment of FIG. 2, an exemplary configuration of atypical isolation point with a double block valve and pressurearrangement is shown. A first block valve 202, such as a metal seatedball valve manufactured by Velan, e.g., Model “Securaseal,” may includea remotely operated motor operated actuator controlled by the batchsequence control computer system. The valve 202 includes positionsensors that transmit an open position signal or a closed positionsignal to the control system input/output 204. For valves in “dirty”hydrocarbon service, a steam purge may be maintained on the valve stemto keep it clean. A similar valve and instrumentation configuration maybe used for the second block valve 206 and control system input/output208. Between the two block valves, a steam header 210 supply purge steamthrough a flow restrictor 212 to maintain a small flow of steam througha pressure instrument tap on the heat traced line 214 between the blockvalves 202 and 206. When both block valves are closed, the steampressure builds up between the block valves to provide steam isolationbetween the two valves. A pressure transmitter 216 on the steam purgeline provides a signal to the batch sequence control system that shouldindicate a high pressure when the block valves are closed and a lowpressure when the block valves are open. The pressure measurementprovides a secondary verification of the position of the double blockvalves. The need for draining condensate from certain blocked sectionsmay be eliminated by installing high temperature heat tracing 214 toprevent steam condensation in the isolation points.

Accordingly, embodiments of the present invention include methods andsystems to meet a high degree of safety integrity by using twoindependent methods in a batch sequence control system to confirmwhether isolation points have been “closed” or “opened.” As a primaryverification, position sensors, such as proximity switches, may be usedto confirm that both isolation valves are in their expected position. Asa secondary verification, a pressure transmitter on the blocked sectionof process piping may be used to confirm that the blocked-in steampressure has increased (if isolated) or decreased (if not isolated). Thedelayed coker, with reference to the embodiment of FIG. 1, may includethe following isolation points with a pressure transmitter monitoringthe pressure between the block valves or isolation valves:

1. feed isolation 160;

2. primary utility isolation 162;

3. secondary utility isolation 164;

4. preheat condensate isolation 166;

5. vapor line quench isolation 168;

6. vent to atmosphere isolation 170;

7. blowdown isolation 172;

8. vapor line isolation 174;

9. antifoam isolation 176;

10. pressure relief device isolation 178;

11. top head isolation 192;

12. bottom head isolation 194;

During operation of the delayed coker batch sequence controller,additional verification using process measurements may include the lossof pressure between pressure relief valve 154 and downstream block valve156 as verification that relief valve is safely open to protect thedrum. The temperature 186 on vapor line water condensate drain betweenblowdown valve 150 and blowdown settling drum may be used to verify thatall water has been drained from the vapor line. The feed line pressure180 may also be used to confirm the water level in the drum and when thedrum has been fully drained of water, as a pressure higher than theoverhead vapor line pressure 182 will indicate a static head of liquidin the drum. Thus, when the difference in pressures has decreased belowa predetermined threshold indicating the drum has been drained asufficient amount in step 17 below, the control system may advance tothe next step 18 and initiate opening of the coke drum top deheadingvalve. The difference in pressures may also be used as a surrogate forthe drum liquid level for a variety of purposes, including monitoringthe level and tracking the rate of drum draining.

In addition, the feed line pressure 180 may also be monitored forcomparison with the utility steam pressure 162. It may be desired tomaintain continuous flow in the feed line after the feed is removed.Ensuring that the utility steam pressure is higher than the hydrocarbonfeed line pressure 180 before closing feed isolation valve 106 allowsthe steam to be cut over into the feed line before the feed is closedand avoid feed material perhaps flowing into the utility steam line.Typically, the feed line pressure may be between 50 and 60 psig, and theutility steam supply header for this service may be about 100 psig. Tocut the steam into the feed line, the steam isolation valve 118 and thesecondary utility isolation valve 122 may be fully opened and then theprimary utility isolation valve 114 may be opened slightly to maintainback pressure on the steam supply. As the back pressure, measured by thepressure transmitter on the common utility header isolation point 162decreases below a predetermined threshold, this verifies that theprimary utility isolation valve 114 has opened and steam is flowing intothe feed line 112. After this verification, the feed isolation valve 106may be closed. The exact thresholds used in the control system may varydepending on the pressures and temperatures of normal operation and theavailable steam supply pressure.

In addition to the built-in verifications of the batch sequencecontroller, the system may also include an integrated safety interlocksystem. The safety interlock system provides double security that thebatch sequence controller will not move a valve that could cause adangerous situation. The safety interlock system also may be active whenthe batch sequence controller is off-line and when the valves aremanually operated from the control system. The safety interlock may usejust the primary verification or both primary and secondary verificationof valve positions described above to confirm the valve positions.

The safety interlock system may utilize a principle of a “clean/dirty”interlock. As used herein, “clean” refers to service primarily incommunication with the atmosphere and “dirty” refers to serviceprimarily in communication with hydrocarbons. This interlock principleensures that (1) no “dirty,” i.e., hydrocarbon, isolation points areopened until all “clean,” i.e., atmospheric, isolation points areconfirmed closed, and (2) no “clean,” isolation points are opened untilall “dirty” isolation points are confirmed closed. The term “isolationpoint” as used herein refers to a double block valve set or an isolationvalve. This interlock may be implemented by identifying the valves thatare the “dirty” hydrocarbon isolation points, identifying the valvesthat are the “clean” atmosphere isolation points, and confirming thatall valves on hydrocarbon isolation points are closed beforetransmitting a signal to open a valve on an atmospheric isolation point;and confirming that all valves on an atmospheric isolation point areclosed before transmitting a signal to open a valve on a hydrocarbonisolation point. The “dirty” isolating valves may include the main feedisolation valve 106, the condensate double block valves 124 and 126, theantifoam double block valves 158 and 160, the overhead quench doubleblock valves 130 and 132, the main vapor line double block valves 138and 140, and the blowdown double block valves 146 and 148. The “clean”isolating valves may include the top head valve 188, the bottom headvalve 190, and the overhead vent double block valves 134 and 136.Optionally, the “clean” isolating valves may include one or more of theprimary utility isolation valve 114, secondary utility isolation valve122 or bottom drain valve 120.

The safety interlock system may be used to ensure that the bottom drainremains isolated from the blowdown lines and the fractionator. This isintended to avoid the back flow of hydrocarbon vapors from either theblowdown or the fractionator into the bottom drain line. This interlockmay be implemented by confirming that either of the bottom drain valve120 and the secondary utility isolation valve 122 are closed before anyone of the main vapor line double block valves 138 and 140 and theblowdown double block valves 146 and 148 are commanded to open. Further,all of the main vapor line double block valves 138 and 140 and theblowdown double block valves 146 and 148 must be confirmed closed beforeboth of the bottom drain valve 120 and the secondary utility isolationvalve 122 may be commanded to be opened.

The safety interlock system may also be used to ensure that the cokedrum cannot be over pressured. An interlock referred to as a “pressurerelief/vent” interlock may ensure that (1) the pressure relief blockvalve cannot be closed until the vent double block valves are confirmedopen, and that (2) the vent double block valves cannot be closed untilthe pressure relief block valve is confirmed open. This interlock may beimplemented by receiving primary verification and secondary verificationthat the vent double block valves are open before transmitting a signalto close the pressure relief block valve; and by receiving primaryverification and secondary verification that the pressure relief blockvalve is open before transmitting a signal to close the vent valves.

The safety interlock system may include other interlock principles asmay be known in the art. Conventionally, interlock safety system were awell-established system developed to normally enhance the manual stepsperformed by the operator during the coke drum cycle. In an embodimentof the present invention, these interlocks remain active at all timesand work within the batch sequence control system so that only thevalves that are allowed to move can operate.

The batch sequence controller automatically operates multiple processvalves to advance the coke drum cycle from one phase to the next. Duringa complete cooking cycle, the major phases include after the drum isfilled, switching feed to the alternate empty drum, steaming out thecoke-filled drum to the fractionators and then to the blowdown,quenching, draining, de-coking and emptying the drum, steaming out theempty drum, preheating the drum, switching the feed valve back to theempty drum, filling the drum with feed, and allowing the coke to form.An exemplary coke drum decoking cycle controlled by the batch controllermay include more detailed steps as follows:

1. switching feed from full drum to empty drum;

2. steaming full drum feed isolation section and feed line;

3. closing feed isolation valve and confirming isolation by twoindependent methods;

4. drying steam to pit, then closing drying valve prior to opening steamto the process;

5. opening steam to the process to achieve “small steam” to thefractionators;

6. depressure full and steaming drum to the blowdown scrubber;

7. isolate (close) drum vapor line to the fractionators;

8. increase steam to the full drum to achieve “big steam” to theblowdown scrubber;

9. start quench water to the full drum;

10. stop steam to the full drum;

11. increase quench water to the full drum;

12. isolate (close) antifoam from the full drum;

13. isolate (close) drum vapor line to the blowdown system;

14. open drum atmospheric vent;

15. isolate (close) pressure relief valves from the full drum;

16. close water to drum;

17. open drain from drum;

18. open top head;

19. open bottom head;

20. decoke drum;

21. close bottom head;

22. close top head;

23. open steam to feed line and bottom drain;

24. close bottom drain;

25. open pressure relief valves on drum;

26. isolate (close) atmospheric vent on drum;

27. drain water from vapor line;

28. isolate (close) steam and secondary utility header from drum;

29. open vapor line valves;

30. open preheat condensate drain;

31. open steam and drain to dry steam on ADJACENT (newly full) drum;

32. isolate (close) preheat condensate from preheated drum;

33. open feed isolation valve;

34. move switch valve from full drum to preheated drum.

In each step of the sequence, preferably just one or two sets of valvesare commanded to move. To advance to the next step, the batch sequencecontrol system requires that primary verification of the valve positionmust be received along with secondary verification of the valve positionas indicated by a monitored process parameters, such as the pressurebetween a double block valve, or a process pressure behind an isolationvalve. In addition, it may be required that other monitored processconditions are satisfied before advancing to the next step.

To facilitate the plant operators in monitoring the automatic sequencingof the coke drum cycle, a graphical representation of the coke drumcycle sequence may be displayed on the operator workstations. One suchrepresentation may be a display of a coke drum sequence matrix thatincludes a column for each of the above detailed steps of the sequence.In each row of the column, the valve positions, the isolation pointsteam pressure and other key process variables may be shown. Colors maybe used to highlight what actions are expected in each step and whatcritical isolations are being formed. The thresholds for the processconditions required to be satisfied in each step may also be shown. Thedisplay may show several steps of the sequence in a single view thatscrolls across the columns as the sequence advances to subsequent steps.To facilitate operator training and manual operation of the delay cokerdrum cycle, the matrix may also be shown completely in a paper form.

Referring to FIG. 3, an illustrative embodiment of a flowchart of theconditions required in one typical step to advance to a next step of thebatch control sequence is shown. While this flowchart is shown as asequence of logical steps, the actual batch sequence control system mayimplement this logic in other sequences or in a parallel monitoring ofconditions requiring satisfaction before advancing to the next step. Forsimplicity of illustration purposes, these conditions are shown in anexemplary sequence in the flowchart shown in FIG. 3. This flowchart maynot coincide with actual implementation that may depend on the selectedcontrol system hardware and software platform configuration.

At the beginning of a batch control sequence Step “N”, step 300, thebatch control system may confirm that selected process parametersmonitored for step “N” are within a predetermined range, or above orbelow a threshold that satisfy the control system logic, step 302. Thebatch control system also may confirm that selected valves monitored asrequired by the control system logic for step “N” are in the correctposition, step 304. Some or all of the process inputs into the controlsystem and the automated valves may be selected to be monitored for agiven step depending on the level of safety requirements. If neither themonitored process parameters nor the monitored process valves are in thecorrect condition, then the control system may transmit an alarm to thecontrol system display, step 306. If the selected process parameters aresatisfied and the selected valves are in the correct position, the batchsequence controller generates a conditional command to close a pair ofdouble block valves X1 and X2, step 308. The control system confirmsthat all other selected valves are in the correct position as requiredby the safety interlock system to permit the commanded valves X1 and X2to close, step 310. If the selected valves are confirmed to be in thecorrect positions then the control system transmits the close command tothe double block valve motor operators, step 312. If the selected valvesare not in the correct position per the safety interlock then thecontrol system transmits alarm status to the control system display,step 306.

As primary verification of valve position, the control system monitorsthe proximity sensors on the block valves that were commanded to closeto confirm that the block valves have moved to the closed position, step314. As secondary verification, the control system also monitors thepressure sensors between the block valves to confirm that the pressurein the process piping between the block valves have increased above apredetermined threshold, step 316. If neither primary verification norsecondary verification is confirmed then the control system transmitsalarm status to the control system display, step 310. For steps that maybe required to be in that state for an extended duration, the batchcontrol system may hold the step until a timer times out, step 320.After the time out, the batch sequence controller may advance to thenext step, step 322. It may be desirable to reconfirm process parametersand valve positions, steps 302 and 304, before proceeding to the nextstep.

After the alarm status has confirmed to be clear either by automaticdetection or operator intervention, step 324, the control system mayreturn to the previous point in the logical operation of step “N” wherethe controller was last engaged before the alarm status conditionoccurred, step 326. If the alarm status is not cleared, then the batchsequence controller will move into an indefinite hold position, step328, requiring operator intervention to clear the alarm conditions andmanually restart the batch sequence controller, or manually operate thecoke drum cycle until the batch sequence controller can put back online.

The batch sequence control logic may be implemented as part of aconventionally known computer control system, such as a distributedcontrol system or a programmable logic controller (“PLC”) controller.The batch sequence control system may include the safety interlocks, orthe safety interlocks may be implemented as a separate system. Forexample, a distributed process control system for the batch sequencecontroller may be implemented on a Delta V control system by EmersonProcess Management. The safety interlock system may be implemented onthe Delta V SIS and integrated with the Delta V distributed controlsystem. The control system may also allow for manual remote operation ofthe coker process unit, but even in manual remote operation the safetyinterlock system may still override the movement of the valves.

One embodiment of a distributed computer control system in a schematicrepresentation is illustrated in FIG. 4. A distributed computer controlsystem 400 may include operator work stations 402 in communication withthe display/input interface 404 of the computer control system 400.Additionally, the operator work stations 402 may include an input deviceconfigured to allow a human operator to interact with any of thecomponents of system. The input device may be a number pad, a keyboard,or a cursor control device, such as a mouse, or a joystick, touch screendisplay, remote control or any other device operative to interact withthe system. These input devices may be useful when the delay coker drumcycle is being manually operated.

The computer control system may include one or more data processors 406in communication with the data interfaces and one or more memory devices408. The one or more data processors 406 may include a centralprocessing unit (CPU), a graphics processing unit (GPU), or both. Theprocessor may be a component in a variety of systems. For example, theprocessor may be part of a standard computer workstation, or a specialcomputer control system or programmable logic controller. The processormay include one or more general processors, digital signal processors,application specific integrated circuits, field programmable gatearrays, servers, networks, digital circuits, analog circuits,combinations thereof, or other now known or later developed devices foranalyzing and processing data. The processors and memories discussedherein, as well as the claims below, may be embodied in and implementedin one or multiple physical chips or circuit combinations. The processormay execute a software program, such as code generated manually (i.e.,programmed).

The memory devices 408 may be a main memory, a static memory, or adynamic memory. The memory may include, but may not be limited tocomputer readable storage media such as various types of volatile andnon-volatile storage media, including random access memory, read-onlymemory, programmable read-only memory, electrically programmableread-only memory, electrically erasable read-only memory, flash memory,magnetic tape or disk, optical media and the like. In one case, thememory may include a cache or random access memory for the processor.Alternatively or in addition, the memory may be separate from theprocessor, such as a cache memory of a processor, the memory, or othermemory. The memory may be an external storage device or database forstoring data. Examples may include a hard drive, compact disc (“CD”),digital video disc (“DVD”), memory card, memory stick, floppy disc,universal serial bus (“USB”) memory device, or any other deviceoperative to store data. The memory may be operable to storeinstructions executable by the processor. The functions, acts or tasksillustrated in the figures or described herein may be performed by theprogrammed processor executing the instructions stored in the memory.The functions, acts or tasks may be independent of the particular typeof instructions set, storage media, processor or processing strategy andmay be performed by software, hardware, integrated circuits, firm-ware,micro-code and the like, operating alone or in combination. Likewise,processing strategies may include multiprocessing, multitasking,parallel processing and the like

The memory 408 may include logic for operating various aspects of thedelayed coker. Batch sequence control logic 410 may be stored incomputer readable form in the memory 408 and includes computerexecutable instructions that when executed by the processor 408 carriesout the method of operating an automated coke drum cycle. For example,the logic may include the method for automatically operating the delayedcoker through all steps of the coke drum sequence, such as describedabove, or in other manners, and include details for a step of thesequence, such as illustrated in FIG. 3. Manual operation logic 412 forthe delayed coker drum cycle may also be stored in memory 408, and maybe executed by the processor 408 to allow manual operation of thedelayed coker. The distributed control system may also include stored inmemory 408 executable process control logic 414 for of other controllingand monitoring other process variables associated with the delayedcoker. The distributed control system may also include data reportingand analytics logic 416 for management reporting of the processoperations data stored in the historical operations database 420. Thedistributed control system may also include a data bus interface 418 forcommunicating with the safety interlock system 422 and the dataacquisition and process control interface 426. The data acquisition andprocess control interface 426 may include the dedicated data acquisitionand control hardware for communication through the field data businterface 428 to the process transmitters 432 and controllers 434 in thedelayed coker.

The safety interlock system 422 may include interlock logic 424 in theform of computer executable logic embodied in computer readablenon-transient memory, or hard-coded in non-volatile memory on dedicatedchipsets in a separate electronic control device, or may be in the formof dedicated electronic circuitry. The safety interlock system 422 maybe a separate system or may be integrated into the main computer controlsystem with the batch sequence controller. The safety interlock system422 may be implemented to override the valve commands transmitted fromeither the batch sequence control operations or from manual controloperations. As such, valve commands submitted under control of either orboth operation systems may pass through the safety interlock system 422before being transmitted to the data acquisition and process controlequipment that includes the valve motor interface 430 to the motoroperated ,or hydraulic operated process valves 436 and 438 in thedelayed coker unit.

Alternatively or in addition, dedicated hardware implementations, suchas application specific integrated circuits, programmable logic arraysand other hardware devices, may be constructed to implement one or moreof the methods described herein. Applications that may include theapparatus and systems of various embodiments may broadly include avariety of electronic and computer systems. One or more embodimentsdescribed herein may implement functions using two or more specificinterconnected hardware modules or devices with related control and datasignals that may be communicated between and through the modules, or asportions of an application-specific integrated circuit. Accordingly, thepresent system may encompass software, firmware, and hardwareimplementations. The methods described herein may be implemented bysoftware programs executable by a computer system. Further,implementations may include distributed processing, component/objectdistributed processing, and parallel processing. Alternatively or inaddition, virtual computer system processing maybe constructed toimplement one or more of the methods or functionality as describedherein.

Although components and functions are described that may be implementedin particular embodiments with reference to particular standards andprotocols, the components and functions are not limited to suchstandards and protocols. For example, standards for Internet and otherpacket switched network transmission (e.g., TCP/IP, UDP/IP, HTML, andHTTP) represent examples of the state of the art. Such standards areperiodically superseded by faster or more efficient equivalents havingessentially the same functions. Accordingly, replacement standards andprotocols having the same or similar functions as those disclosed hereinare considered equivalents thereof.

As will be understood by persons skilled in the art, the processconditions of a delayed coker may vary greatly depending on the exactcoker equipment and piping configuration, as well as the variations ofthe feed material and desired product. The above detailed description isfor illustrative purposes, and is not intended to be restrictive. Theteachings herein may be applied by those skilled in the art to beimplemented on a variety of delayed coker units. Therefore, theinvention is defined by the claims appended hereto and include otherinventions not claimed that may be explicitly or inherently disclosed inthis application, including all equivalents, modifications andenhancements thereto.

1-4. (canceled)
 5. A method for automatic operation of a delayed cokercomprising one or more pairs of coke drums, the method comprising:operating the one or more pairs of coke drums in alternating cycles offilling a first drum of a pair with heated feed material while emptyinga second drum of the pair; initiating an automatic batch sequencecomputer control system configured to automatically operate one or moresets of double block valves, each set of double block valves including afirst valve and a second valve positioned along process piping betweenthe first drum of the pair and the second drum of the pair, wherein theprocess piping connects the one or more pairs of coke drums withadditional components of the delayed coker through a sequence of stepsfor a complete coke drum cycle; and in one step of the cycle:transmitting a command to close a set of the double block valves;monitoring position sensors on the set of double block valves as aprimary verification to confirm the double block valves are both closed;monitoring a pressure at a valve isolation point between the set ofdouble block valves to confirm the pressure between the double blockvalves has increased above a predetermined threshold as a secondaryverification to confirm the double block valves are both closed;confirming that the double block valves are both closed based on theprimary verification; confirming that the double block valves are bothclosed based on the secondary verification; and then advancing thecontrol system to a next step of the coke drum cycle.
 6. The method ofclaim 5, further comprising: in another step of the cycle: transmittinga command to open the set of double block valves; monitoring theposition sensors on the double block valves as a primary verification toconfirm the double block valves are both open; confirming that thedouble block valves are both open based on the primary verification;monitoring the pressure at the valve isolation point between the doubleblock valves to confirm the pressure between the double block valves hasdecreased below a predetermined threshold as a secondary verification toconfirm the double block valves are both open; confirming that thedouble block valves are both open based on the secondary verification;and then advancing the control system to another next step of the cokedrum cycle.
 7. The method of claim 6, wherein the set of double blockvalves are coke drum overhead vent double block valves and the positionsensors are located on the set of coke drum overhead vent double blockvalves, the method further comprising: receiving signals from theposition sensors on the set of coke drum overhead vent double blockvalves that confirm the double block valves are open; receiving a signalfrom a pressure transmitter monitoring a pressure on the process pipingbetween the overhead vent double block valves that confirms the pressurehas decreased below a predetermined threshold; and then transmitting asignal to close a pressure relief block valve.
 8. The method of claim 6,further comprising: receiving signals from position sensors on apressure relief block valve that confirms the pressure relief blockvalve is open; receiving a signal from a pressure transmitter monitoringa pressure on the process piping between the pressure relief block valveand a pressure relief valve that confirms the pressure has decreasedbelow a predetermined threshold; and then transmitting a signal to closeoverhead vent double block valves.
 9. The method of claim 5, furthercomprising: transmitting a signal to open a bottom drain valve to drainliquid from the coke drum; receiving a signal from a first pressuretransmitter monitoring a pressure on a feed line process piping;receiving a signal from a second pressure transmitter monitoring apressure on an overhead vapor line process piping; calculating adifference between pressures on the feed line and the overhead vaporline; after the difference in pressure between the pressure on the feedline process piping and the pressure on the overhead vapor line processpiping decreases below a predetermined threshold that indicates the cokedrum is drained of a sufficient amount of liquid, advancing the controlsystem to a further step; and in the further step transmitting a commandto open a top deheading valve on the coke drum.
 10. The method of claim5, further comprising: receiving a signal from a first pressuretransmitter monitoring a pressure on a steam supply line; when feedmaterial is flowing through a feed line, receiving a signal from asecond pressure transmitter monitoring a pressure on the feed line;calculating a difference between pressures on the steam supply line andthe feed line; confirming the difference in pressure exceeds apredetermined threshold that indicates the steam pressure is greaterthan the feed line pressure; transmitting a signal to open a steamsupply valve connecting with the feed line; verifying the steam supplyvalve is open; and then transmitting a signal to close a feed isolationvalve.
 11. A computer control system for carrying out the method ofclaim 6, the system comprising: a delayed coker comprising: two or morecoke drums operating in pairs in alternating cycles of filling one drumwith heated feed material while emptying the other drum; at least oneset of double block valves positioned along process piping between twoor more of the coke drums, wherein the process piping connects the cokedrums with additional components of the delayed coker; position sensorson the double block valves; a device to monitor pressure between thedouble block valves; a processor in communication with an operator workstation, wherein the processor is configured to: initiate the automaticbatch sequence; transmit the command to close the set of double blockvalves; monitor the position sensors on the double block valves as theprimary verification to confirm the double block valves are both closed;monitor the pressure at a valve isolation point between the double blockvalves as the secondary verification to confirm the double block valvesare both closed; confirm that the double block valves are both closedbased on the primary verification; confirm that the double block valvesare both closed based on the secondary verification; advance the controlsystem to the next step of the coke drum cycle; transmit the command toopen the set of double block valves; and a memory in communication withthe processor, the memory having stored thereon computer executableinstructions that when executed by the processor perform the method. 12.The control system of claim 11, further comprising a safety interlocksystem in communication with the control system, the safety interlocksystem comprising logic encoded on memory that when executed performsthe method of: identifying a plurality of valves as hydrocarbonisolation points; identifying a plurality of valves as atmosphereisolation points; confirming that all valves on a hydrocarbon isolationpoint are closed before transmitting a signal to open a valve on anatmospheric isolation point; and confirming that all valves on anatmospheric isolation point are closed before transmitting a signal toopen a valve on a hydrocarbon isolation point.